Ciprofloxacin (CPX) is a fluoroquinolone antibiotic used for treating respiratory, urinary tract, gastrointestinal and abdominal infections. There are only a limited number of studies related to neurological adverse effects of this drug in therapeutic doses. Therefore, in the present study, we aimed to investigate the influence of CPX, when administered at pharmacological doses, on behavioral parameters of rats and the probable underlying mechanisms. CPX was administered in single oral daily doses of 20 and 50 mg/kg for 14 days in rats. CPX-induced depression and anxiety were evaluated by modified forced swimming test and elevated plus maze test, respectively. Also, spontaneous locomotor activity and motor coordination were assessed by activity cage and Rota-rod apparatus. Effects of CPX administration on brain serotonin, dopamine, γ-amino-butyric acid (GABA), glutamate, adrenaline and noradrenaline levels were determined by high performance liquid chromatography (HPLC) analysis. Contribution of oxidative stress to the changes induced by CPX administration was evaluated by measuring brain catalase, superoxide dismutase, glutathione (GSH) and malondialdehyde (MDA) levels. Our results indicated that depression-like and anxiety-like behaviors were observed only in the 50 mg/kg CPX-administered group with simultaneous decreases in the brain serotonin and GABA levels. In addition, in the brain homogenates of CPX-administered groups, increased MDA as well as decreased GSH and catalase activity with respect to their controls, indicated enhanced oxidative stress and weakened antioxidant defense system. In conclusion, repeated pharmacological doses of CPX were found to induce neurological toxicity. Also, altered brain neurotransmitter levels and increased oxidative stress observed in our study were thought to be the possible underlying mechanisms of ciprofloxacin-induced neurotoxicity.

Agomelatine is an antidepressant with a distinct pharmacological mechanism of action as an MT1 and MT2 receptor agonist and as a 5-HT_2C receptor antagonist. We evaluated the chronic effects of agomelatine administration (40 mg/kg, 20 weeks) on the cognitive performance of rats in the Morris water maze task. We applied unbiased stereological quantification methods to estimate the total numbers of granular and pyramidal neurons located in the dorsal hippocampus. We also analyzed the dendritic spines of pyramidal neurons in the CA1 region using the Golgi–Cox impregnation method. The agomelatine-treated group found the hidden platform more quickly than did the control group and spent significantly more time in the target quadrant. Agomelatine administration caused significant volumetric and numerical enhancements in granular and pyramidal neurons in the dentate gyrus and CA1–3 subregions, respectively. Increased densities of the mushroom and stubby types of spines, with no alteration in the thin-shaped spines, were observed in the agomelatine-treated group. These results showed that long-term agomelatine administration induced a nootropic effect supported by structural changes. Enhancement of the more stable types of dendritic spines might indicate improved adaptive capacity in hippocampal neurons. Future studies will provide a better understanding of the effect of this drug on synaptic plasticity.

Researches that are related to the central nervous system complications of diabetes have indicated higher incidence of cognitive disorders in patients. Since the variety of nootropic drugs used in clinics is limited and none of them consistently improves the outcomes, new and effective drug alternatives are needed for the treatment of diabetes-induced cognitive disorders. Based on the nootropic potential of agomelatine, the promising efficacy of this drug on cognitive impairments of diabetic rats was investigated in the current study. Experimental diabetes model was induced by streptozotocin. After development of diabetes-related cognitive impairments in rats, agomelatine (40 and 80 mg/kg) was administrated orally for two weeks. Cognitive performance was assessed by Morris water-maze and passive avoidance tests. Then, the total numbers of neurons in both dentate gyrus and Cornu Ammonis (CA) 1–3 subfields of the hippocampus were estimated by the optical fractionator method. Agomelatine treatment induced notable enhancement in the learning and memory performance of diabetic rats. Moreover, it reversed the neuronal loss in the hippocampal subregions of diabetic animals. Obtained results suggest that agomelatine has a significant potential for the treatment of diabetes-induced cognitive impairments. However, therapeutic efficacy of this drug in diabetic patients suffering from cognitive dysfunctions needs to be confirmed by further clinical trials.